This work proposes a method that can be used to control the transverse profile of the optical intensity distribution of a diode-end-pumped solid-state laser operating with a Gaussian seed beam. The transverse gain profile in an external amplifier was temporally adjusted to control other higher-order intensity distribution. The amplifier is dual pumped by two independent diode lasers. The higher-order intensity distribution profile was created within the amplifier by independently adjusting the dual diodes output powers. This technique will permit synchronised variation of both the output power of the laser and the transverse intensity distribution of a laser beam.
Lasers beams with a specific intensity profile such as super–Gaussian, Airy or Dougnut-like are desirable in many applications such as laser materials processing, medicine and communications. We propose a new technique for laser beam shaping by amplifying a beam in an end-pumped bulk amplifier that is pumped with a beam that has a modified intensity profile. Advantages of this method are that it is relatively easy to implement, has the ability to reshape multimode beams and is naturally suited to high power/energy beams. Both three and four level gain materials can be used as amplifier media. However, a big advantage of using three level materials is their ability to attenuate of the seed beam, which enhances the contrast of the shaping.
We first developed a numerical method to obtain the required pump intensity for an arbitrary beam transformation. This method was subsequently experimentally verified using a three level system. The output of a 2.07 μm seed laser was amplified in a Ho:YLF bulk amplifier which was being pumped by a 1.89 μm Tm:YLF laser which had roughly a TEM10 Hermit Gaussian intensity profile. The seed beam was amplified from 0.3 W to 0.55 W at the full pump power of 35 W. More importantly, the beam profile in one transverse direction was significantly shaped from Gaussian to roughly flat-top, as the model predicted. The concept has therefore been shown to be viable and can be used to optimise the beam profile for a wide range of applications.
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